Ever wonder whether your baby can really see her crib mobile, or whether your cell phone ring alarms her? The fact is, infants perceive things very differently than adults do. Some senses, like touch and hearing, are fully developed at birth. Others, such as sight, take several months to mature. We'll tell you what to expect and what you can do to stimulate each of your baby's senses.

Vision

Your newborn sees contrasts, like black and white, most easily and sees objects most clearly from eight to 12 inches away -- about the distance to your face during breastfeeding. "He can't focus both across the room and up really close," says Nicholas J. Tapas, M.D., a pediatrician in Glenview, Illinois. By 6 weeks, your infant's vision should improve to the point where he can spot you from 15 to 20 feet away. His eye muscles are getting stronger around this time, too, and he'll soon be able to track your finger when you move it in front of his face. By 4 months, he can make out less-contrasting colors clearly. And by the time he's walking and crawling, between 8 and 12 months, he'll be able to use his depth perception to judge distances as he explores.

What you can do: Decorate the nursery in bright colors and bold patterns. Change the position of your baby's bassinet and feed him on both sides to help get him used to seeing from different angles. Start playing games like pat-a-cake and peekaboo at about 4 months to help his hand-eye coordination.

Hearing

A baby's hearing starts to develop while she's still in the womb, so your child will be familiar with your voice when she's born, says Peter Jung, M.D., chair of pediatrics at Houston's Memorial Hermann Memorial City Hospital. She may startle when a door slams because newborns are sensitive to changes in sound. But once she's asleep don't be surprised if she snoozes through even the loudest noises, says pediatrician Laura Jana, M.D., coauthor of Heading Home With Your Newborn: From Birth to Reality. At first, your infant will be easily distracted by background noise, but gradually she should start to focus on speech and will try to imitate you by cooing and babbling. By around 6 months, she may mimic specific sounds you make.

What you can do: Talk to your child to encourage her language development. Try using a singsong-y voice to get her attuned to the different tones and patterns in speech, recommends Stephen J. Marquis, M.D., a pediatrician in Appleton, Wisconsin. For babies who have trouble getting to sleep, turn on a white-noise machine; it's soothing because it replicates the low, steady sounds of the womb.

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Touch

Touch is one of the best-developed senses at birth -- and it's absolutely crucial to bonding. Cuddling your baby will make him feel warm and secure, as will swaddling because it re-creates the confined feeling of the womb. And, yes, babies explore through touch, and their preferred tool is their mouth. So don't worry if he sucks or chews on anything he can get his hands on, Dr. Jana says. Just make sure you give him things that are safe and clean.

What you can do: Hold your baby often. Skin-to-skin contact is especially therapeutic for newborns, doctors say. Simply rubbing on some lotion after a bath is soothing, too, or you can try some gentle massage moves.

Smell

Your baby has a good sense of smell from the start. She gets to know your scent on Day 1 and probably recognizes the scent of other people in her life within about a week. "Babies are especially sensitive to the smell of breast milk and can even distinguish it from formula," says Dr. Tapas. This can cause problems around 3 or 4 months, when it's time for them to start sleeping through the night. If you come in to comfort your baby, just know she'll smell you and may want to be fed.

What you can do: Dr. Marquis recommends using the same products regularly, because babies like familiarity. But nix heavily scented products while you're breastfeeding. Smell and taste are closely linked, and your baby may not nurse as well if she's taking in heavy doses of your perfume.

Taste

Infants prefer sweet flavors and dislike anything that's sour or bitter. By about 4 months, they start to recognize spiciness and saltiness, Dr. Jung says. Studies have shown that babies can taste various flavors from their mothers' diets in breast milk, so eating a wide range of foods while nursing will help your child get used to those tastes early on.

What you can do: Eat a variety of foods while breastfeeding, and feed your baby lots of different flavors and textures as soon as he starts solids -- it may help discourage him from becoming a picky eater later in life.

Afraid Something's Wrong?

If you suspect that your baby has a vision or hearing problem, take her to the pediatrician to get checked out ASAP. Hearing loss is the most common congenital problem, and diagnosing it early is especially vital because it can interfere with learning language. Dr. Nicholas J. Tapas recommends whispering in each of your baby's ears: If she giggles or wiggles after you whisper into one ear but not the other, something may be wrong. Many states require hospitals to do a hearing screening at birth, which should catch some potential problems, and the American Academy of Pediatrics recommends that all infants have their eyes checked at the hospital. If your baby didn't have an eye exam, have her tested by 6 months. Until then, look for asymmetry between the eyes, excessive redness or discharge, drooping eyelids, and abnormally shaped pupils (check your baby in an evenly lit room).